A huge fire erupted in Moscow-annexed Crimea after a suspected drone attack hit an oil depot on Saturday, as fighting intensified on the southern Ukrainian front and shelling deprived Russian border villages of power.
The attacks came one day after Kyiv said preparations for a long-awaited counteroffensive were nearly complete, having vowed to expel Russian forces from territory they seized in the east and south following their 2022 invasion.
On Friday, a Russian strike on a bloc of flats in the central Ukrainian city of Uman killed 23 people, including a baby boy.
On Saturday, officials in Moscow-controlled Crimea, towns under Russian occupation in southern Ukraine and a governor of a border region reported attacks.
Fears of Ukrainian reprisals more than a year into Moscow's offensive have grown in Russia, where a range of cities have canceled traditional May 9 celebrations to mark Soviet victory over the Nazis at the end of World War II in 1945.
In Sevastopol, home to Russia's Black Sea Fleet, clouds of smoke rose high into the sky as fuel reserves burned.
The port city has been hit by a series of drone attacks since Moscow's invasion of Ukraine began more than a year ago.
Russian-installed authorities said the fire was caused by a suspected drone but sought to play down the incident, amid rising security fears on the peninsula.
The Kremlin said nothing about the attack.
It came less than 24 hours after Russia struck a typical Soviet-era housing bloc in the historic city of Uman, killing more than two dozen of its residents.
Ukraine's President Volodymyr Zelensky, in his evening address on Saturday, said six children had been killed in the attack — the previous figure given by the authorities had been five.
"We will do everything possible to ensure that the terrorist state is held accountable for its actions as soon as possible," he added.
"Anyone who prepares such rocket attacks cannot but know that they will become an accomplice to murder," said Zelensky.
The Ukraine leader said that next week would be important in terms of "our struggle for justice."
He stressed that Kyiv was preparing "several important, powerful steps to consolidate our partners and give more energy to the creation of a tribunal for the crime of Russian aggression. And to accelerate the defeat of the terrorist state."
Earlier Kyiv had identified an 18-month-old baby boy as among the victims.
"One woman is considered missing. The search continues," Ukrainian Interior Minister Ihor Klymenko said.
Ukraine did not claim the Crimea attack, but military intelligence implied it was revenge for Uman.
Andriy Yusov, from the defense ministry's intelligence unit, said it was "God's punishment, in particular for the civilians killed in Uman."
He warned people in Crimea to "avoid being near military facilities and facilities providing the aggressor's army in the near future."
On the Russian-annexed peninsula, the governor of Sevastopol, Mikhail Razvozhayev, urged Crimeans to "remain calm" and said "nobody was hurt."
He estimated the fire was "around 1,000 square meters" (10,764 square feet).
Razvozhayev insisted that the peninsula's reserves had not been impacted and that authorities had enough fuel for all civilian needs.
Earlier this week, Moscow said it had repelled a drone strike on Crimea — annexed by Russia in 2014 and used as a launchpad for its invasion.
In southern Ukraine, Russian occupation authorities said a key city they control — Novaya Kakhovka — had come under "intense shelling" and had been cut off from power.
The city fell to Russian forces on the first day of their invasion on Feb. 24, 2022. It lies in the part of the Kherson region that Moscow still controls, having withdrawn from the eponymous regional capital last November.
Russian forces urged people in the city "to keep calm," saying that work to restore power would start "after the shelling ends."
Russian border villages shelled
The shelling of Novaya Kakhovka came a day after Russian shelling killed a 57-year-old woman in a southern Ukrainian village. Zelensky had promised a response.
Inside Russia, security fears an expected Ukrainian counteroffensive.
The governor of the border Belgorod region — also been hit by several attacks during the course of the war — said Saturday that five frontier villages were without power after Ukrainian shelling.
"The power lines are damaged," Gladkov said, adding that there had been no victims.
Elsewhere, Russia accused Poland — with whom it has historically poor relations — of a "blatant violation" of international norms after Warsaw impounded a school run by the Russian embassy in the Polish capital.
Moscow called the move an "illegal act" and promised "harsh" consequences against Warsaw.